I have a 1998 ford f150 5.4 engine 155,000 miles. When I'm at a stop sign or just idling my truck lopes and feels like it could die. I changed the fuel filter and cleaned the air filter but that didn't help. What could be wrong.

 

That's a bit of a broad question. What else have you tried? Plugs? Coils? Cleaned MAF? checked for vacuum leaks?

 

going by the info given i'd say the iac needs cleaning or replacing. is there a cel?

 

ive got a 2000 F150, 5.4L triton......was experiencing same problems with idle, except mine i had to keep my rpm's at @500 to keep it from dieing. i replaced the IAC and the problem went away. Id check that."check engine" light on?

 

A... it happened all at once. Its vry likely a vac leak. Check all those little plastic vac lines all over the place. Pay close attention to the large rubber vac hose coming out of the very back of the tbody elbow. Its tough to find and even tougher to check or change but that little sucker has a bad habbit of rotting and caving in or cracking appart all together. If no luck there try shooting tbody cleaner at the tbody gasket in short bursts with the straw on. start at one spot and work your way around. listen for the rpms to jump (the truck needs to be running) this is will indicate a break in the gasket causing a vac leak.

B... its been getting worse slowly and now it has just gotten to bad to ignore.
you may need a full tune up. Plugs, wires if you have them. and very likely a good thorough throttle body cleaning! youl fine plenty on that in this forum. i just did mine at 105k and got an insane ammount of crud out of it.

Incase it isnt obvious i just went through this myself...

Good Luck!!! Cheers!

 

I had the same issue on my 97 with 4.6 engine.
I Replaced the Idle control valve ( $80 bux ) Issue resolved.

 

Idle Air Control Valve.